New Solar Panels Use Waste Heat to Purify Water

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Solar panels can bring electricity to remote areas, and photovoltaic technology has improved in recent years. However, many of these regions also have limited access to clean water. A new type of solar power setup developed at King Abdullah University of Science and Technology in Saudi Arabia could address both of those issues. These panels leverage waste heat from solar panels to distill and purify water.

The researchers used salt water to test the technology, but it should work equally well on fresh water that simply isn’t fit for human consumption. The solar panels sit on top of a multi-layer box where they can absorb sunlight and generate power. Below that is a three-stage distillation unit.

There’s nothing particularly special about the solar panels used in the system. About 10 percent of the sunlight hitting the photovoltaic cells goes toward generating power. While much higher efficiencies have been demonstrated in the lab, most commercial cells are only a little more efficient. However, those panels aren’t also generating water.

As the panels pull in solar radiation to make power, some of the energy radiates out as waste heat. The King Abdullah University of Science and Technology design directs that heat down into the first layer of water purification. It heats seawater, causing it to evaporate and re-condense as clean, fresh water. The heat generated by the first layer passes through a membrane into the second distillation layer where it purifies more water, and it’s the same for the third (bottom) layer. It’s essentially a very fancy stacked solar still — the researchers note the solar panel design purified three times as much water as a solar still, and you get electricity, too.

According to the team, water passed through the device comes out safe for drinking by all measurable standards. The levels of lead, copper, sodium, calcium, and magnesium after filtration are all below the thresholds set by the World Health Organization.

You might be able to deploy a more efficient solar power farm and water purification rig as separate systems, but the system developed by these researchers could be a major breakthrough because it can do both at the same time. The team sees this as an ideal solution for remote areas where people have limited power and ample access to undrinkable water. With more efficient solar panels, they say, this system could eventually generate 10 percent of the world’s fresh water.